Explicitly set enum type values.
Explicitly set enum type values.

Summary: As in title.

Reviewed By: yangchi, lnicco

Differential Revision: D21440640

fbshipit-source-id: a3b918b4fe8f9ad463aaea6ebdf2c5846af0e9b1

facebookincubator/mvfst,facebookincubator/mvfst,facebookincubator/mvfst,facebookincubator/mvfst,facebookincubator/mvfst